We propose to develop a toolbox for estimation, simulation and control of multi-joint movements. Our immediate goal is to facilitate research in Motor Control, by providing access to advanced computational methods and making such methods an integral part of the hypothesis generation-and-testing cycle. The estimation component of the toolbox will enable researchers to accurately compute multi-joint movement trajectories as well as limb sizes from motion capture data, without spending hours to place markers at precise locations and redesign setups to ensure that every marker is always visible. The control component will make it possible to formulate mathematically-sound hypotheses about the control strategies used by the brain, and automatically synthesize detailed control laws corresponding to the user's hypotheses. These control laws will then be applied to realistic musculo-skeletal models, using the simulation component, and the predicted behavior will be compared to experimental data in terms of kinematics, contact forces and EMGs. In case of a mismatch the toolbox will be able to netune any free parameters of the controller, and also search the library of candidate control strategies and identify the one which best agrees with the data. Our longer-term goal is to assist clinicians and engineers designing new treatments such as reconstructive surgery and functional electric stimulation. Testing candidate control mechanisms on simulated musculo-skeletal dynamics can greatly reduce the undesirable trial-and-error iterations. Customizations necessary for clinical use are left outside the scope of this project, however they will be possible once the core functionality is developed in a system with open design. The toolbox will be written in Matlab, with some C++ components, and will be freely available for academic, research and non-prot purposes. Project narrative We propose to develop a toolbox for estimation, simulation and control of multi-joint movement. Our immediate goal is to facilitate research in the eld of Motor Control by providing access to advanced computational methods presently beyond the reach of many investigators. While tools for simulating musculo-skeletal dynamics already exist, simulation alone is rarely suffcient to advance our understanding of motor function. Here we will combine simulation with automatic controllers capable of driving realistic musculo-skeletal models, and provide tools for estimating multi-joint movements from motion capture data. Our longer-term goal is to assist clinicians and engineers designing new treatments such as reconstructive surgery and functional electric stimulation.